[PATCH RFC 02/11] rust: lock: Add Lock::pin_init()

Asahi Lina
2023-07-14T09:32:21Z

Allow initializing a lock using pin_init!(), instead of requiring
the inner data to be passed through the stack.

Signed-off-by: Asahi Lina <lina@asahilina.net>
---
rust/kernel/sync/lock.rs | 30 +++++++++++++++++++++++++++++-
rust/kernel/sync/lock/mutex.rs | 13 +++++++++++++
2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index a2216325632d..d493c5d19104 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -6,7 +6,9 @@
//! spinlocks, raw spinlocks) to be provided with minimal effort.

use super::LockClassKey;
-use crate::{bindings, init::PinInit, pin_init, str::CStr, types::Opaque, types::ScopeGuard};
+use crate::{
+ bindings, init::PinInit, pin_init, str::CStr, try_pin_init, types::Opaque, types::ScopeGuard,
+};
use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned};
use macros::pin_data;

@@ -87,6 +89,7 @@ pub struct Lock<T: ?Sized, B: Backend> {
_pin: PhantomPinned,

/// The data protected by the lock.
+ #[pin]
pub(crate) data: UnsafeCell<T>,
}

@@ -111,6 +114,31 @@ pub fn new(t: T, name: &'static CStr, key: &'static LockClassKey) -> impl PinIni
}),
})
}
+
+ /// Constructs a new lock initialiser taking an initialiser.
+ pub fn pin_init<E>(
+ t: impl PinInit<T, E>,
+ name: &'static CStr,
+ key: &'static LockClassKey,
+ ) -> impl PinInit<Self, E>
+ where
+ E: core::convert::From<core::convert::Infallible>,
+ {
+ try_pin_init!(Self {
+ // SAFETY: We are just forwarding the initialization across a
+ // cast away from UnsafeCell, so the pin_init_from_closure and
+ // __pinned_init() requirements are in sync.
+ data <- unsafe { crate::init::pin_init_from_closure(move |slot: *mut UnsafeCell<T>| {
+ t.__pinned_init(slot as *mut T)
+ })},
+ _pin: PhantomPinned,
+ // SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
+ // static lifetimes so they live indefinitely.
+ state <- Opaque::ffi_init(|slot| unsafe {
+ B::init(slot, name.as_char_ptr(), key.as_ptr())
+ }),
+ }? E)
+ }
}

impl<T: ?Sized, B: Backend> Lock<T, B> {
diff --git a/rust/kernel/sync/lock/mutex.rs b/rust/kernel/sync/lock/mutex.rs
index 923472f04af4..06fe685501b4 100644
--- a/rust/kernel/sync/lock/mutex.rs
+++ b/rust/kernel/sync/lock/mutex.rs
@@ -18,6 +18,19 @@ macro_rules! new_mutex {
};
}

+/// Creates a [`Mutex`] initialiser with the given name and a newly-created lock class,
+/// given an initialiser for the inner type.
+///
+/// It uses the name if one is given, otherwise it generates one based on the file name and line
+/// number.
+#[macro_export]
+macro_rules! new_mutex_pinned {
+ ($inner:expr $(, $name:literal)? $(,)?) => {
+ $crate::sync::Mutex::pin_init(
+ $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!())
+ };
+}
+
/// A mutual exclusion primitive.
///
/// Exposes the kernel's [`struct mutex`]. When multiple threads attempt to lock the same mutex,

--
2.40.1